The economic consensus is that groups behave in a more self-regarding way than individuals, which affects their members’ decision-making. This column describes new evidence from experiments in Slovakia and Uganda that supports an alternative hypothesis from social psychology that simply being a member of a group makes us more anti-social to outsiders. Within-group cohesion in organisations may also have a dark side, fostering hostility to outsiders.

Three attributes are often suggested to generate cooperative behaviour – a good heart, good norms, and intelligence. This column reports the results of a laboratory experiment in which groups of players benefited from learning to cooperate. It finds overwhelming support for the idea that intelligence is the primary condition for a socially cohesive, cooperative society. Warm feelings towards others and good norms have only a small and transitory effect.